Because perfluorochemicals have the ability to releasably bind oxygen, perfluorochemical preparations have been evaluated for use as blood substitutes and as ischemic modifiers. Such perfluorochemical preparations are typically prepared by emulsifying the perfluorochemical compound in an aqueous medium to form a perfluorochemical emulsion. Perfluorochemical emulsions are free of infectious agents and antigens, and their use obviates the need for blood typing of the recipient.
Although perfluorochemicals are chemically inert, they appear to adversely affect blood platelets and clotting factors. This adverse effect is believed to be due to the low surface tension of perfluorochemicals.
In an effort to avoid the adverse effect of perfluorochemicals on blood platelets and clotting factors, perfluorochemical emulsion particles are coated with a lipid, such as lecithin Emulsions containing lipid-coated perfluorochemical particles are, for example, disclosed in U.S. Pat. Nos. 3,962,439, 4,252,827, 4,423,077 and 4,497,829.
The prior-art perfluorochemical emulsions do not have a sufficiently high level of stability to withstand sterilization at elevated temperatures followed by storage in the liquid state at room temperature. Thus, their storage life in an unfrozen state is shorter than desired.